The present invention relates generally to needle-free or needleless injection systems and more specifically to such a system that is particularly well suited for being used a single time and then being disposed.
Needle-free systems have been in use for many years. Some such systems have used a pressurized gas to power a hypodermic jet injection. The related technology includes a number of teachings for gas-powered injection devices, including: U.S. Pat. No. 4,596,556 to Morrow, et al.; U.S. Pat. No. 4,913,699 to Parsons; U.S. Pat. No. 5,730,723 to Castellano, et al.; and WIPO publication WO 97/3705 naming Weston and Thornlea as inventors.
It is also known in this art to provide a needle-free injection system having two plungers that are initially spaced adjacent either end of a glass drug storage sleeve, with liquid drug being disposed between the plungers within the sleeve. Such a system also includes a plastic drug storage chamber disposed coaxially with and forwardly of the glass drug storage sleeve. The forward end of the plastic drug chamber terminates in an injection orifice. The plastic drug chamber includes an enlarged portion that permits drug to flow past the forward plunger when that plunger is aligned with the enlarged portion.
In this prior system, axial force is exerted on the rear plunger immediately prior to injection. Because liquid drug is disposed in the space between the plungers, the plungers move in unison in a forward direction until the forward plunger is aligned with the enlarged portion. At that point, the continued forward travel of the rearward plunder forces liquid drug around the forward plunger until all of the drug is disposed in the plastic drug chamber forward of both plungers, which are now in abutment. The unit thus is ready for actuation. When this prior unit was actuated, the plungers both exerted a forward axial force, causing liquid drug to be directed out of the injection orifice and into the patient.
The invention described in my earlier application, referenced above, is similar to the present invention except that the prior invention, which is not prior art, included more parts and therefore would likely be more expensive to fabricate. This may be more than a theoretical drawback, given that in many applications the user may need to purchase units in quantity because each unit is normally designed to be used only one time prior to disposal.
One form of the present invention provides a needle-free injection system including the following components: a cartridge for holding liquid drug prior to injection, the cartridge having a rear end and a front end; a plug mounted to the front end of the cartridge, the plug including a channel; a displaceable valve positioned within the channel prior to injection; and a nozzle portion for receiving liquid drug from the glass cartridge for injection, the nozzle portion including an injection orifice and a drug chamber having a valve seat designed to receive the valve to facilitate injection of liquid drug through the injection orifice.
Another aspect of the invention provides a needle free injector with the following components: a housing for holding various injector components; a gas cartridge mounted in the housing for providing a source of pressurized gas; a mechanism for piercing the gas cartridge upon demand, the mechanism being mounted in the housing such that it is moveable with respect to the gas cartridge; a drug cartridge mounted in the housing for storing liquid drug prior to injection; the drug cartridge having a plunger initially positioned at a rearward portion thereof; an injection orifice defined in a front end of the housing and having a fluid inter connection with the drug cartridge; a gas piston for converting gas pressure from the gas cartridge into a forward force exerted on the plunger; and a seal system mounted in the housing for preventing pressurized gas leaving the pierced gas cartridge from reaching the gas piston prior to injection.
A third aspect of the invention provides a method for filling a cartridge with liquid drug for use in a needle-free injection device. The method includes the following steps: providing a plug with a front and a rear and having a rearwardly extending portion and a central channel; positioning a valve in the central channel at a point set back from the front of the plug; providing a cylindrical glass drug cartridge having a front and a rear; positioning a plunger in the rear end of the cartridge; filling the cartridge with liquid drug; and inserting the plug with the valve disposed therein in the front end of the cartridge, and simultaneously having the rearwardly extending portion displace some of the liquid drug in the cartridge so that the liquid drug enters the channel, displacing the valve forwardly within the channel.